Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting TVs and Video Sources
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 02-20-2021, 04:52 PM   #1
Daveleone
Senior Member
 
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 153
Default Vizio VO42L, white logo, no backlight, no picture

Hi all! I've got a Vizio VO42L. Plug it in, and logo flashes orange/white for a bit, then solid orange. Press power, and logo changes to white. There is no backlight.
From reading some of the posts here I thought the inverter could have been the problem, but I've replaced it and still have the same issue. I noted that shining a flashlight on the screen shows nothing, so now I'm thinking main board?

I took the following readings with the TV powered on. I also tried taking the readings with the CFL connectors unplugged - no change.

Main board:
Continuity across F1 & F2 = GOOD
F1 = 5.12v
F2 = 11.57v

PSU Connector 1 (J21?):
24V = 24v
SGND = 0v
A = 0v
B = 0v
C = 0v

PSU Connector 2 (J22?):
PSON= 3.27v
12V = 11.57v
SGND = 0v
5VSB = 5.16v
A = 0v
B = 0v
C = 0v

Inverter:
Continuity across F1 = GOOD
Left leg @ Q7 & Q9 = cycles between 0v-1.2v
Middle leg @ Q7 & Q9 = 24.96v
Right leg @ Q7 & Q9 = cycles between 0v-1.2v
Top leg @ Q8 & Q10 = 0v
Middle leg @ Q8 & Q10 = cycles between 0v-1.2v
Bottom leg @ Q8 & Q10 = 0v
Voltages @ connectors to CFLs = 0v

Do you think I got a second bad inverter? Or do I have a bad main board? What should I try next?

Thanks in advance for your help!
--Dave
Attached Images
File Type: jpg back.jpg (751.1 KB, 10 views)
File Type: jpg psu.jpg (659.4 KB, 6 views)
File Type: jpg psu_closeup_1.jpg (428.1 KB, 6 views)
File Type: jpg psu_closeup_2.jpg (435.8 KB, 5 views)
File Type: jpg main.jpg (919.8 KB, 7 views)
File Type: jpg main_closeup.jpg (597.6 KB, 8 views)
File Type: jpg inverter.jpg (772.7 KB, 5 views)
File Type: jpg inverter_closeup_1.jpg (464.7 KB, 4 views)
File Type: jpg inverter_closeup_2.jpg (674.1 KB, 5 views)
File Type: jpg inverter_closeup_3.jpg (620.6 KB, 4 views)
File Type: jpg inverter_closeup_4.jpg (465.8 KB, 7 views)

Last edited by Daveleone; 02-20-2021 at 05:03 PM..
Daveleone is offline   Reply With Quote
Old 02-21-2021, 11:38 AM   #2
dick_barton
Badcaps Veteran
 
dick_barton's Avatar
 
Join Date: Aug 2015
City & State: Cardiff
My Country: Wales
Line Voltage: 230V AC, 50Hz
I'm a: Hobbyist Tech
Posts: 6,227
Default Re: Vizio VO42L, white logo, no backlight, no picture

What voltages do you have on the Inverter Board connector
1, 2, 3, 4 & 5 =
6, 7, 8, 9 & 10 =
11 =
12 =
13 =
14 =

Is the white fuse F1 showing continuity?
__________________
Willing to help but I'm no expert.
dick_barton is offline   Reply With Quote
Old 02-21-2021, 06:58 PM   #3
Daveleone
Senior Member
 
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 153
Default Re: Vizio VO42L, white logo, no backlight, no picture

Quote:
Originally Posted by dick_barton View Post
What voltages do you have on the Inverter Board connector
1, 2, 3, 4 & 5 =
6, 7, 8, 9 & 10 =
11 =
12 =
13 =
14 =

Is the white fuse F1 showing continuity?
That connector is directly connected to PSU Connector 1 (J21?), so:
1-5 = 24v
6-14 = 0v
I double checked the voltages just to be sure the cable was good.

F1 does have continuity.
Daveleone is offline   Reply With Quote
Old 02-22-2021, 05:13 AM   #4
dick_barton
Badcaps Veteran
 
dick_barton's Avatar
 
Join Date: Aug 2015
City & State: Cardiff
My Country: Wales
Line Voltage: 230V AC, 50Hz
I'm a: Hobbyist Tech
Posts: 6,227
Default Re: Vizio VO42L, white logo, no backlight, no picture

Can you provide a close up of what's given in the red box please.
The Inverter On signal appears to be missing.
Attached Images
File Type: jpg inverter.jpg (1.34 MB, 9 views)
dick_barton is offline   Reply With Quote
Old 02-22-2021, 10:41 AM   #5
Daveleone
Senior Member
 
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 153
Default Re: Vizio VO42L, white logo, no backlight, no picture

Quote:
Originally Posted by dick_barton View Post
Can you provide a close up of what's given in the red box please.
The Inverter On signal appears to be missing.
Yes, I think you're right.
12: VOnOff is 0V

What should that voltage be? Should I jumper it to some other pin to see if the backlight will come on?

Thanks!
Attached Images
File Type: jpg inverter_closeup5.jpg (263.1 KB, 5 views)
Daveleone is offline   Reply With Quote
Old 02-22-2021, 12:57 PM   #6
dick_barton
Badcaps Veteran
 
dick_barton's Avatar
 
Join Date: Aug 2015
City & State: Cardiff
My Country: Wales
Line Voltage: 230V AC, 50Hz
I'm a: Hobbyist Tech
Posts: 6,227
Default Re: Vizio VO42L, white logo, no backlight, no picture

You need to check where the VonOff signal comes from. I would expect it to be around 3V when VonOff = On
Have you checked the two fuses shown in photo 6 of 11 in your first post.

Last edited by dick_barton; 02-22-2021 at 01:02 PM..
dick_barton is offline   Reply With Quote
Old 02-22-2021, 01:48 PM   #7
Daveleone
Senior Member
 
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 153
Default Re: Vizio VO42L, white logo, no backlight, no picture

Quote:
Originally Posted by dick_barton View Post
You need to check where the VonOff signal comes from.
That wire is connected to "B" on the PSU Connector 1 (J21?) (photo 3 of 11 in my first post)

Quote:
Originally Posted by dick_barton View Post
Have you checked the two fuses shown in photo 6 of 11 in your first post.
Main board:
Continuity across F1 & F2 = GOOD
F1 = 5.12v
F2 = 11.57v
Daveleone is offline   Reply With Quote
Old 02-27-2021, 03:33 PM   #8
Daveleone
Senior Member
 
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 153
Default Re: Vizio VO42L, white logo, no backlight, no picture

Quote:
Originally Posted by dick_barton View Post
You need to check where the VonOff signal comes from. I would expect it to be around 3V when VonOff = On
Have you checked the two fuses shown in photo 6 of 11 in your first post.
I jumpered PSU Connector 2 (J22?) 5VSB to PSU Connector 2 "B" (which connects to Inverter Connector VOnOff). The backlight comes on with both inverters that I have. So, the main board appears to be the problem.
Anything else I should check on the main board? Or should I just order a replacement?
Daveleone is offline   Reply With Quote
Old 02-28-2021, 01:30 AM   #9
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 39,116
Default Re: Vizio VO42L, white logo, no backlight, no picture

I would start checking LDO Voltage Regulator IC's on the main board.

There is Main board repair kit and EEPROM also.
https://www.shopjimmy.com/search.php...ery=Vizio+VO42
__________________
Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
budm is offline   Reply With Quote
Old 03-06-2021, 10:04 AM   #10
Daveleone
Senior Member
 
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 153
Default Re: Vizio VO42L, white logo, no backlight, no picture

Just to close this out, I was able to get a replacement main board for $20 from ElectroParts, so I decided to order it and save my time (instead of working on the defective board). The replacement main board worked.
Daveleone is offline   Reply With Quote
Old 03-06-2021, 10:27 AM   #11
nomoresonys
Badcaps Veteran
 
Join Date: Jan 2013
City & State: midwest
My Country: U.S.
I'm a: Knowledge Seeker
Posts: 6,459
Default Re: Vizio VO42L, white logo, no backlight, no picture

Thanks for the feedback Dave.
__________________
Signature: Any Stooge can find an "Idiot" by looking in his mirror.
nomoresonys is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2021
Powered by vBulletin ®
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 05:01 AM.
Did you find this forum helpful?